Hi,
I can`t claim to be an expert on the Titane, but I know it was a popular model in the 80s. They are quite rare in the UK but crop up often on German eBay so I guess they were popular there. The value of yours depends on the condition; it is well worth getting a battery in it to prove it works! Have a look on eBay to see what they are fetching if you want to sell it. The style is unusual and is very much a matter of taste. Personally, I like them and I`d consider buying one at some time to add to my Omega collection.
cheers,
Paul